Abstract

Antibiotics such as amoxicillin and cephalexin are a group of pharmaceutical compounds in human medicine
practice that have been entered in water bodies. Presence of these compounds in the environment has raised concerns regarding the toxicity to aquatic organisms and the emergence of strains of antibiotic-resistant bacteria. Removal of these substances before entering the aquatic environment as well as water reuse plant is very important. The objective of this investigation was to evaluate the impact of hydrophilic and hydrophobic fractions of Natural Organic Matter (NOM) on the removal efficiency of cephalexin and amoxicillin, by using two different commercially available composite NF membranes (TFC-SR2 and TFC-SR3). In addition, the effect of NOM fractions on retention mechanism and permeates flux behavior was studied. Amoxicillin and cephalexin were used
as models of antibiotics; alginate and humic acid were used as models of hydrophilic and hydrophobic fractions of NOM, respectively. It was observed that the rejection and permeate flux of amoxicillin and cephalexin were influenced by the membrane characteristics and properties of NOM. The results showed that as the alginate proportion was increased, the rejection improved. The permeate flux decreased with increasing alginate ratio. It was observed that the rejections of amoxicillin and cephalexin in TFC-SR2 were >97.3% and >95.8% in all experiments, respectively. In TFC-SR3,the rejection percentage were (95.9%-100%) and (86.1%-96.3%),
respectively. Alginate and humic acid had synergistic effect on flux decline. In other words, increasing alginate
concentration increased the rate and extent of flux reduction.